WASHINGTON (AP) -- The Obama administration is warning American businesses about an unusually potent computer virus that infected Iran's oil industry.

The warning comes even as suspicions persist that the U.S. government is responsible for secretly creating and unleashing such cyberweapons against foreign countries.

Unlike a bullet or missile fired at an enemy, a cyberweapon that spreads across the Internet may circle back accidentally to infect computers it was never supposed to target.

It's one of the unusual challenges facing the programmers who build such weapons, and presidents who must decide when to launch them.

The Homeland Security Department's warning about the new virus, known as "Flame," assures U.S. companies that no infections have been discovered so far inside the U.S.

AP-WF-06-02-12 1139GMT